1. Field of the Invention
The present invention relates to a video data processing system and, more particularly, to a video data processing system consisting of one or more devices and adapted to send a high-speed scanned image signal from a CRT or the like to a low-speed recording device.
2. Related Background Art
Recording devices such as printers have been recently proposed to receive image data directly from a CRT and provide a hard copy. However, since image data from the CRT has a high speed, a buffer memory for storing data of a few main scanning lines is arranged in a conventional video data processing system. The CRT image is processed as a still image and the CRT data is stored in the buffer memory. After recording (printing) of the first few lines is completed, the data of the first few lines is erased and data of the next few lines is then stored in the buffer memory. Printing is repeated in this manner to provide a hard copy of the CRT screen image. This conventional recording scheme requires a long period of time for printing a one-frame image. In particular, when a color image is to be printed, a large number of data are required. In addition, in association with a printing scheme, printing requires a longer period of time. For example, a one-frame CRT image of 640.times.400 dots requires four minutes to be printed out as a hard copy. For this reason, the throughput of the host computer is decreased. Moreover, it takes a longer period of time to print out a color CRT image. Therefore, there is no room for practical applications in the conventional video data processing systems.
On the other hand, in order to receive a one-frame scanned CRT image so as to achieve high-speed video data processing, a large-capacity, expensive memory must be used. In addition, hardware for controlling high-speed processing must also be used, which is uneconomical.
Furthermore, there are no conventional video data processing systems which allow processing of scanned image signals having different signal levels and different image sizes as well as outputting thereof.